Time Sheet Calculator

Level: Intermediate 30–60 min

Concepts: Algorithms

Solutions: C# | TypeScript | Python

You are to develop a simple time sheet calculator application. It must take a start time in HH:mm format and an end time in HH:mm format. It must also take an optional break duration in HH:mm format to represent the duration of lunch. The result must be emitted in HH:mm format.

All times must be in 24-hour time format, no AM/PM.

Allow for users to invert the start and end times and still calculate the result properly.

Examples

Examples
Start Time : 08:42
End Time: 16:20
Break Duration : 00:30
Result : 07:08
Start Time : 17:02
End Time: 02:09
Break Duration : 00:35
Result : 08:32
Start Time : 07:02
End Time: 16:22
Result : 09:20

Hint

You may not use Timespan of other built-in DateTime capabilities to do this kata.

Bonus

  1. Allow for three and 4 digit numbers to be entered without needing a : to separate HH from mm. a. If three digits assume H:mm format.
  2. Allow for the user to input AM/PM instead of only using 24-hour time. E.g 08:00 AM

Reference Walkthrough

Reference implementations in C#, TypeScript, and Python live at tddbuddy-reference-katas/timesheet-calc. This is an F2 (light builder) kata: one primary entity (Timesheet), a typed Day enum distinguishing weekdays from the weekend, named constants for the overtime threshold and standard work week, a TimesheetTotals record whose totalHours is derived, and a test-folder TimesheetBuilder().WithEntry(day, hours).Build().

Scope note — weekly hour totals only. The original prompt above is a single-day HH:mm parser; the reference reframes the kata to its natural F2 shape — a weekly timesheet with daily and weekend overtime classification. HH:mm parsing, inverted/overnight times, 3-and-4-digit bonuses, AM/PM support, hourly pay rates, and PTO/holiday categories are deliberately out of scope for this reference and listed as stretch goals in the repo README. Those either return the kata to F1 string-parsing territory or tip it into F3 collaborator territory.

Overtime rules. Weekday hours beyond 8 are overtime. Weekend hours (Saturday / Sunday) are always overtime. A full Monday–Friday at 8 hours each produces the 40-hour standard work week with no overtime. Fractional hours are permitted; negative hours raise a language-idiomatic error with the cross-language-identical message "hours must not be negative".

This kata ships in Agent Full-Bake mode at middle gear, the F2 (light builder) tier. See the repo’s Gears section for why middle gear is the deliberate choice.